Lenticular foil, which is also referred to as lens raster foil, is a clear, transparent foil, on the front side of which there is a plurality of curvatures, which are disposed next to one another. The curvatures extend parallel to one another and act as optical lenses. These foils are used to produce lenticular products, for example, for realizing image sequences or three-dimensional image impressions. For this purpose, the back of the lenticular foil is imprinted with a subject. Subsequently, opaque white is applied or the foil is laminated on cardboard.
In order to be able to realize image sequences or three-dimensional image impressions, it is necessary to divide different images into strip-shaped image parts and to combine these sequentially into a single subject. In this connection, each strip sequence of all the images that are to be combined has exactly the same width as a lens strip and must be printed exactly underneath it. Only in this way, depending on the viewing angle selected, does the desired image effect come about, that is, the becoming visible of image sequences or of the 3-dimensional impression of the image. The product is useless if the strip sequences are not printed directly under the lens strip.
In sheet-processing machines, it is generally customary to align the sheets for processing according to their front edge in that these are guided with the front edge against feeding marks. Subsequently, the sheet, which has been aligned according to the front edge, is aligned according to the side edge. For this purpose, the sheet is shifted transversely to its running direction and transported with its side edge against a side stop (DE 100 47 314 A1).
From the DE 102 05 630 A1, it is furthermore known that, after the sheet is aligned in its running direction, the actual position of the side edges is determined by measuring means and compared with the nominal value. If the actual value deviates from the nominal value, a control signal is generated and supplied to a control device. The control device is connected with a gripper system, which is mounted in a feed cylinder so that it can be displaced in the axial direction. The nominal position of the side edge is then realized by shifting the gripper system.
If the sheets of lenticular foil reach the processing stage so that the lens structure extends transversely to the running direction of the sheets and, with that, parallel to the front edge of the sheets, they are aligned according to the front edge at the front marks. Subsequently, they are aligned according to the side edge and afterwards transported in the gripper bite by the sheet-processing machine. Since the front edge of the sheet of lenticular foil does not necessarily always proceed precisely with the lens structure of the lenticular foil, qualitatively bad or useless products cannot be excluded. In addition, it is necessary, by manual adjustment manipulations, to assign the strip sequences accurately to the lens strip. As a result, the productivity of the machine as a whole is also affected disadvantageously.